1. Field of the Invention
The present invention relates to a ground device for preventing static electricity to improve the electrical stability of a head drum apparatus for use in a magnetic tape recording and reproducing apparatus. More particularly, the invention relates to a ground device of a head drum apparatus capable of making the assembly and disassembly operations of the ground device components simpler and easier, thereby resulting in an increased productivity and an improved service efficiency thereof.
2. Description of the Prior Art
Conventionally, a shaft-rotating type of head drum apparatus has been employed in a magnetic tape recording and reproducing apparatus.
In the shaft-rotating type of head drum apparatus, a rotating shaft is pressed and fitted into an upper drum, and a lower drum is rotatably mounted on a lower portion of the rotating shaft. A motor is attached to the bottom surface of the lower drum and activated to rotate the shaft, and hence the upper drum. A head provided in the upper drum records a signal to or reproduces a signal from a magnetic tape.
However, the head drum apparatus of shaft-rotating type has two degrees of freedom and does not fully overcome resonant vibration problems so that it cannot eliminate the likelihood of malfunction due to resonant vibration upon the rotation of the upper drum.
Recently, in order to solve the above problems, a fixed-shaft type of head drum apparatus has been proposed. The typical constitution of the fixed-shaft type of head drum assembly is burdened by certain disadvantages.
Specifically, a ground device must necessarily be employed with the head drum apparatus in order to prevent static electricity, and resultant electrical instability, from developing in the apparatus. However, such a ground device is necessarily of such a structure as to make it difficult to attach to the drum apparatus, and it is also likely to become detached therefrom after a certain period of use. In addition, disassembly of the ground device is necessarily difficult and time consuming because it is necessary to disassemble the entire head drum apparatus in the process.
Thus, there is a need for the development of a ground device of a head drum apparatus which is not burdened by the above disadvantages.
It is, therefore, a primary object of the present invention to provide a ground device of a head drum apparatus capable of making the assembly of the ground components thereof simpler and easier, thereby resulting in increased productivity thereof.
It is another object of the present invention to provide a ground device of a head drum apparatus capable of making the disassembly of the components simpler and easier, thereby resulting in improved service efficiency.
In accordance with the present invention, there is provided a head drum apparatus which comprises: a lower drum; a stationary shaft pressed and fitted into a center hole of the lower drum; an upper drum rotatably coupled to the stationary shaft via at least one bearing; a boss fixed to the top portion of the stationary shaft by means of a set-screw; a motor rotor mounted to the top surface of the upper drum; a motor stator fixed to the boss, the motor stator being disposed opposite to the motor rotor; a ground device, including an anchor member, anchored to the upper surface of the boss with an elastic member fixed to the bottom surface of the anchor member, the elastic member extending downwardly through a bore in the boss; and a ground member fixed to the lower end of the elastic member, the ground member being in elastic contact with an outer race of an upper bearing.
Preferably, the anchor member has a hole into which the stationary shaft is fitted, whereby the anchor member is prevented from moving unintentionally when it is anchored to the boss. Preferably, the elastic member is a compressed coil spring.